1. Field of the Invention
The present invention concerns a crosslinked type layered metal phosphonate compound and a production process therefor, a non-crosslinked type layered metal phosphonate compound and a production process therefor, as well as a stock solution. More specifically, the invention relates to a novel multi-ingredient crosslinked type and non-crosslinked type layered metal phosphonate compound that can be used, for example, as adsorption materials, ion exchange materials, electrolyte materials, etc. and a production process therefor, as well as a stock solution used for the production of the crosslinked type and non-crosslinked type layered metal phosphonate compound described above.
2. Description of the Related Art
A crystalline organic hexacoordinate metal phosphonate compound has a two dimensional layered structure in which a metal oxide octahedron having a hexacoordinate metal atom as a central atom (M) and a phosphonic acid tetrahedron are connected by sharing oxygen atoms. Particularly in a case where the central atom (M) is a hexacoordinate metal atom capable of taking a tetravalence, the crystalline organic hexacoordinate metal phosphonate compound has an α-type or γ-type layered structure.
For example, the α-type layered structure of the crystalline organic zirconium phosphonate has a layered structure in which zirconium atoms present uniformly on a plane are connected two dimensionally by sharing oxygen atoms with the bottoms of phosphonic acid tetrahedrons present therebetween alternatively above and below. Accordingly, planes in which phosphonic acid tetrahedrons are arranged with the top being directed outward and a plane in which oxide octahedrons formed with zirconium atoms are arranged constitute a 2:1 layered structure. Since organic groups connected by a P—C bond are present at the outer apexes of the tetrahedrons, organic groups derived from phosphonic acid are present on both surfaces of the 2:1 layer.
On the other hand, the γ-type structure has a composite plane in which two planes where zirconium atoms present uniformly and alternately on two planes are connected alternately by sharing four oxygen atoms of PO4 tetrahedron are connected with a phase being displaced from each other. The zirconium atoms of the composite plane are further connected by sharing two oxygen atoms with phosphonic acid tetrahedrons present on the layer surface, to provide a layered structure forming zirconium oxide octahedrons. Accordingly, organic groups derived from phosphonic acid are present on both surfaces of the layer.
Theoretically, in the α-type, three apexes of each of the organic phosphonic acid tetrahedrons are bonded with three different zirconium atoms. Further, each of the zirconium atoms is bonded with oxygen atoms of different six phosphonic groups to form an octahedron.
By optimizing the type of the organic group of the organic phosphonic acid, the layered zirconium phosphonate can be used, for example, as adsorbent materials, ion exchange materials, electrolyte materials, etc.
A phosphoric acid in which the organic group of the phosphonic acid is replaced with an OH group forms a zirconium phosphate by reacting with a metal source such as ZrOCl2.8H2O. However, it has been known long since that the method of merely reacting starting materials does not form the 2:1 layer but forms an amorphous gel, and the structural stability is low. A layered zirconium phosphate of high structural stability and high crystallinity was obtained for the first time by A. Clearfield in 1964 by refluxing in a 12M phosphoric acid for a long time. In 1978, G. Alberti found that a layered zirconium phosphate of extremely high crystallinity was obtained by using an HF catalyst for the reaction. M. B. Dines applied the HF catalyst to the reaction between the organic phosphonic acid and ZrOCl2.8H2O to obtain a layered organic zirconium phosphonate in 1980. Further, a method of carrying out reaction between various types of organic phosphonic acids and ZrOCl2.8H2O by a hydrothermic reaction or HCl or HBr catalytic reaction has also been known. A method of using hydrothermic reaction or a method of HCl or HBr as a catalyst has a merit in that the layered structure has crystallinity to some extent and a plurality types of organic phosphonic acids can be introduced uniformly to the 2:1 layer.
Those layered organic zirconium phosphonates in which the organic group has a sulfonic group function as electrolytes. Since the sulfonation product of the layered organic zirconium phosphonate has a two dimensional (layered) structure of inorganic materials as a main chain and sulfonic groups on the side chain ingredient, they have a feature that the durability to hydrogen peroxide by-produced during fuel cell reaction is higher compared with polyperfluoro sulfonation products typically represented by Nafion (registered trade mark), or hydrocarbon type sulfonation products such as crosslinked type polystyrene sulfonic acid, and sulfonated polyether ether ketone (S-PEEK).
For sulfonation products of non-crosslinked type layered zirconium phosphonate, while various proposals have been made so far, sulfonation products of the non-crosslinked type layered organic zirconium phosphonate have a drawback that they are soluble to water.
On the other hand, in a case of using an organic diphosphonic acid for the starting material, a crosslinked type layered zirconium phosphonate in which the 2:1 layers are crosslinked to each other with the organic diphosphonic acid. However, while many examples on the sulfonation products of water soluble non-crosslinked type layered zirconium phosphonate have been reported, there are scarce reports on sulfonation products of crosslinked type layered zirconium phosphonate that are insoluble to water.
For example, Non-Patent Documents 1-3 disclose sulfonation products of crosslinked type layered zirconium phosphonate obtained by reacting Zr4+compound, an organic diphosphonic acid ((HO)2OP—C6H4—C6H4—PO(OH)2, or (HO)2OP—C6H4—C6H4—C6H4—PO(OH)2), or an organic diphosphonic acid and an inorganic monophosphonic acid (HPO(OH)2) as a second ingredient under the presence of an HF catalyst and then sulfonating the organic diphosphonic acid ingredient by a post reaction.
The documents describe that    (1) an aromatic sulfonic acid moiety is present only in the organic diphosphonic acid ingredient (crosslinking ingredient),    (2) a monophosphonic acid introduced at first as P—H is oxidized to P—OH by the step of sulfonation in the post reaction, and    (3) HF as a catalyst is taken as Zr—F in zirconium phosphonate.
Further, Pantet Document 1 discloses a crosslinked type layered zirconium phosphonate obtained by;
(1) reacting ZrOCl2.8H2O and 1,4-phenylene diphosphonic acid ((HO)2OP—C6H4—PO(OH2)), and inorganic phosphonic acid (H3PO3) under the presence of an HF catalyst, and
(2) reacting the resultant product and phenylene-3-sulfo-1-phosphonic acid ((HO)2OP—CH6H4—SO3H).
The document describes that the relative ratio for the phenylene diphosphonic acid, phenylene phosphonic acid-sulfonic acid, and inorganic phosphonic acid in the solid obtained by the method is 1.20:0.56:1.
Non-Patent Document 4 discloses a method of synthesizing phenylene-3-sulfo-1-phosphonic acid ((HO)2OP—CH6H4—SO3H). The document describes    (1) reacting phenyl phosphonic acid ((HO)2OP—C6H5) with 2.4 equivalent amount of SO3 in CH2ClCH2Cl at 84° C. for 24 hr,    (2) repeating the procedure of adding BaCl2.2H2O to the reaction solution and recovering excess sulfuric acid as BaSO4 by precipitation, and    (3) regenerating products of free acid by an ion exchange resin, thereby capable of isolating phenylene-3-sulfo-1-phosphonic acid.
Patent Document 2 discloses a homopolymer Zr(O3—P—R—SO3H)2 of various sulfonated zirconium phosphonates. The document describes that    (1) zirconium 3-sulfopropyl phosphonate is obtained by adding HF to an aqueous solution containing ZrOCl2.8H2O dissolved therein and dropping the same to an aqueous solution of 3-sulfopropyl phosphonic acid,    (2) zirconium 2-sulfoethyl phosphonate is obtained by adding an aqueous solution of ZrOCl2.8H2O to 2-sulfoethyl phosphonic acid hydrolyzed with HBr and refluxing the same for 1.5 hr and    (3) zirconium 2-(sulfophenyl)ethyl phosphonate is obtained by treating an aqueous solution containing 2-(sulfophenyl)ethyl phosphonic acid with an aqueous solution of ZrOCl2.8H2O and HF.
Further, Patent Document 3 describes that zirconium phenyl phosphonate (Zr(O3PC6H5)2) is obtained by adding phenyl phosphonic acid and HCl to an aqueous solution of ZrOCl2.8H2O although this is not a sulfonation product.
Further, Patent Document 4 discloses various types of layered metal phosphonate compounds represented by the general formula M(O3P—R)2 obtained by reacting ZrOCl2.8H2O, Th(NO3)4.4H2O, PbO2, UCl4, TiCl4, or Ce(HSO4), and a phosphonic acid such as chloromethyl phosphonic acid ((HO)2OPCH2Cl), 2-mecarpto ethyl phosphonic acid ((HO)2OPCH2CH2SH), or 2-sulfoethyl phosphonic acid ((HO)2OPCH2CH2SO3H).
Further, Patent Document 5 discloses a copolymer of zirconium phosphonates containing two types of phosphonic acid ingredients.
[Non-Patent Document 1] A. Clearfield, et al., J. Solid State Chem. 167, 376 (2002)
[Non-Patent Document 2] A. Clearfield, et al., Reactive Polymer, 5, 13 (1987)
[Non-Patent Document 3] A. Clearfield, et al., J. Am. Chem. Soc., 2003, 125, 103754.
[Non-Patent Document 4] G. Alberti. et al., J. Chem. Soc. Dalton Trans., 1819 (1989)
[Patent Document 1] G. Alberti, et al., EP0736539/2001 (Japanese Patent Unexamined Publication No. H09-20507)
[Patent Document 2] U.S. Pat. No. 4,235,991
[Patent Document 3] U.S. Pat. No. 4,267,308
[Patent Document 4] U.S. Pat. No. 4,436,899
[Patent document 5] U.S. Pat. No. 4,429,111
In a case of synthesizing a layered zirconium phosphonate, when HF is used as a catalyst, a soluble intermediate reaction product ZrF6 is formed and reaction with an organic phosphonic acid proceeds moderately. Accordingly, this can avoid precipitation of fine particle products caused by violent reaction and provide an advantage of greatly promoting the development of the layered structure. However, the method involves a problem that when reaction is conducted by using various types of phosphonic acids, synthesis of a multi-ingredient type layered zirconium phosphonate with uniform introduction of them is difficult to be synthesized. That is, since the starting composition of the phosphonic acid cannot be reflected on copolymerized composition of the product, the structural design of the copolymer is difficult. It is considered that this is attributable to the large difference of the reactivity of the intermediate reaction product ZrF6 to different types of phosphonic acids. As a result, it tends to form a mixture of a plurality of compounds each containing a single phosphonic acid not a single compound containing the multi-ingredient phosphonic acid. Further, in a case of using HF as the catalyst, a portion of fluorine atoms remains in the form of Zr—F in the compound to possibly result in environmental problems.
Further, a method of synthesizing a layered zirconium phosphonate by using hydrothermic reaction, HCl catalytic reaction, or HBr catalytic reaction has an advantage capable of synthesizing a multi-ingredient zirconium phosphonate in which the crystallinity of the layered structure is high to some extent and, in addition, multi-ingredient layered zirconium phosphonate where a plurality types of phosphonic acids are introduced uniformly can be synthesized.
However, such methods involve a problem that the crystallinity of the layered structure cannot be improved so much. The trend is remarkable, particularly, in the case of the hydrothermic reaction. Further, in a case of the HCl catalytic reaction and HBr catalytic reaction, it involves a problem that acid mists are generated during synthesis.
Further, for the method of synthesizing a sulfonation product of a layered zirconium phosphonate, a method of synthesizing a layered zirconium phosphonate not having a sulfonic group and then sulfonating the phosphonic acid ingredient (post-sulfonation) has been known.
However, the post-sulfonation is difficult to control and it may possibly result in corruption of the layered structure if the reaction conditions are severe. Further, in a case of synthesizing the layered zirconium phosphonate, when a monophosphonic acid having a substituent instable to the post-sulfonation is used, the substituent of the monophosphonic acid ingredient is sometimes lost upon post-sulfonation. Accordingly, the degree of freedom for the structure design is low.
For solving the problems, it may be considered to use a sulfonated phosphonic acid as the starting material. For example, since a sulfonation product of an aliphatic phosphonic acid can be purified to a high level, a product of high crystallinity is obtained by synthesizing a zirconium phosphonate using the same.
However, an isolation procedure of a sulfonated phosphonic acid is generally troublesome extremely. Further, the isolation procedure has not yet been established for many sulfonated phosphonic acids. For example, since sulfonation products of aromatic phosphonic acids have high boiling points, isolation by distillation is difficult. Further, since the isolation procedure by an ion exchange is troublesome, it is difficult to obtain a highly pure sulfonation product. Accordingly, when a zirconium phosphonate is synthesized by using the same, only the product of low crystallinity can be obtained. Lowering of the crystallinity causes lowering of stability against hydrolysis.
Further, in the crosslinked type layered zirconium phosphonate disclosed in Patent Document 1, a portion of the organic diphosphonic acid ingredient not consumed in the crosslinking reaction is present at the layer surface. In a case of reacting such a crosslinked type layered zirconium phosphonate and metasulfophenylene phosphonic acid, not-crosslinked organic diphosphonic acid ingredient present at the layer surface is substituted by the metasulfophenylene sulfonic acid ingredient due to the surface exchange reaction. Accordingly, this involves the problem that sulfonic groups cannot be introduced between the layers.
Since the existent synthesis methods involve the various problems as described above, examples on the crosslinked type layered zirconium phosphonate having three or more phosphonic acid ingredients or crosslinked type layered zirconium phosphonate containing two or more types of phosphonic acid ingredients having the sulfonic group have not been reported. Further, examples on the crosslinked type layered metal phosphonate compounds containing two or more types of phosphonic acid ingredients and in which the central atom of the metal oxide octahedron includes other metal than Zr have not been reported.
In the same manner, due to the problem as described above in the existent synthesis methods, examples on the report on the multi-ingredient non-crosslinked type layered metal phosphonate compound having two or more types of ingredients have not been reported. Further, examples on the non-crosslinked type layered metal phosphonate compounds containing two or more types of phosphonic acid ingredients having a sulfonic group have not been reported.